NMR methods are used to analyze sample compositions or to determine the structure of substances in samples. NMR spectroscopy is an efficient method of instrumental analysis. In some NMR methods, the sample is exposed to a strong, static magnetic field B0 in a z-direction. In the process, the magnetic field interacts with the nuclear spin of the sample material, in particular the nuclear spin of the sample aligns with the static magnetic field B0. High-frequency (HF) electromagnetic pulses are radiated into the sample in the x- or y-direction, e.g. orthogonal to the static magnetic field. The temporal development of this nuclear spin of the sample in turn generates high-frequency electromagnetic fields which are detected in the NMR apparatus. Information regarding the properties of the sample can be obtained, over a specific spatial region, from the detected HF fields. In particular, the chemical composition and the chemical bonding relationships in the sample can be concluded from the position and intensity of NMR lines
The analysis sample generally comprises a cylindrical sample tube that typically has a circular, oval, or rectangular cross section and contains the solid or liquid measurement substance. The sample tube is closed at least at the side by which it first penetrates into the probe, and is typically located in a spinner. The sample tube and the spinner are transported into the probe from outside the magnet, e.g., using a transport system. As described herein, the insertion opening is located at the top on the probe, and the sample tube is inserted into the probe from the top. It is also conceivable, however, to insert the sample tube and/or spinner into the probe from below, into an opening provided therefor. This case is analogous to that mentioned above and will not be described explicitly, for reasons of clarity. When the sample tube is in the measuring position, the spinner is inside the turbine, which allows the sample tube to rotate.
Conventional “standard bore” probes currently available may be fastened to a shim system by means of two screws. This is very inconvenient for the user, since the user typically crawls under the magnet in order to mount the probe and works kneeling down. In addition, the relatively small screws are generally inconvenient due to the mounting position of the probe on the magnet and can normally be tightened only using a special screwdriver.
When the fastening screws are tightened, the connection is fixed and can no longer be adapted to later position changes, which may be caused by temperature changes, for example. These position changes may cause mechanical backlash or unacceptable axial tension between the probe and the retention system.
Conventional “wide bore” probes are typically mounted on the retention system using a quick-release fastener. Due to the link form of the typical clamping system, the maximum force is applied to the probe when the clamping ring is operated at the very start of the mounting process. After this maximum force has been overcome, the system relaxes and the probe may be mounted to the shim system of the NMR apparatus with an undefined force until a backlash arises that is possibly outside of acceptable tolerances.
In order to prevent these difficulties, a user will typically individually adjust the retaining elements to the relevant shim system for each probe. However, the user may not be able to control the force that is set in the process. It is merely possible to check whether or not mechanical backlash exists, whether within tolerances or not.
These circumstances typically preclude the use the quick-release fastener already known from the “wide bore” probes to mount “standard bore” probes, since the “standard bore” probes generally require that there should be no backlash at all and relatively low force between the probe and the shim system.
In addition, the known quick-release fasteners of “wide bore probes generally provide no form of locking against inadvertent opening. However, “standard bore” probes may require the positive locking feature due to safety considerations and marketing considerations.